The following related patent applications, assigned to the same assignee hereof and filed on even date herewith in the names of the same inventors as the present application, disclose related subject matter, with the subject of each being incorporated by reference herein in its entirety:
Memory Module with Hierarchical Functionality, Ser. No. 09/775,477; High Precision Delay Measurement Circuit, Attorney Docket No. 37079/B600/JFO; Single-Ended Sense Amplifier with Sample-and-Hold Reference, Attorney Docket No. 37362/B600/JFO; Limited Switch Driver Circuit,Attorney Docket No. 37361/B600/JFO; Fast Decoder with Asynchronous Reset with Row Redundancy; Attorney Docket No. 37115/B600/JFO; Diffusion Replica Delay Circuit, Attorney Docket No. 37360/B600/JFO; Sense Amplifier with Offset Cancellation and Charge-Share Limited Swing Drivers, Attorney Docket No. 37363/B600/JFO; Memory Architecture with Single-Port Cell and Dual-Port (Read and Write) Functionality, Attorney Docket No. 37364/B600/JFO; Memory Redundancy Implementation, Attorney Docket No. 37496/B600/JFO; and; A Circuit Technique for High Speed Low Power Data Transfer Bus, Attorney Docket No. 37497/B600/JFO.
1. Field of the Invention
The present invention relates to memory devices, in particular, semiconductor memory devices, and most particularly, scalable, power-efficient semiconductor memory devices.
2. Background of the Art
Memory structures have become integral parts of modern VLSI systems, including digital signal processing systems. Although it typically is desirable to incorporate as many memory cells as possible into a given area, memory cell density is usually constrained by other design factors such as layout efficiency, performance, power requirements, and noise sensitivity.
In view of the trends toward compact, high-performance, high-bandwidth integrated computer networks, portable computing, and mobile communications, the aforementioned constraints can impose severe limitations upon memory structure designs, which traditional memory system and subcomponent implementations may fail to obviate.
One type of basic storage element is the static random access memory (SRAM), which can retain its memory state without the need for refreshing as long as power is applied to the cell. In an SRAM device, the memory state II usually stored as a voltage differential within a bistable functional element, such as an inverter loop. A SRAM cell is more complex than a counterpart dynamic RAM (DRAM) cell, requiring a greater number of constituent elements, preferably transistors. Accordingly, SRAM devices commonly consume more power and dissipate more heat than a DRAM of comparable memory density, thus efficient; lower-power SRAM device designs are particularly suitable for VLSI systems having need for high-density SRAM components, providing those memory components observe the often strict overall design constraints of the particular VLSI system. Furthermore, the SRAM subsystems of many VLSI systems frequently are integrated relative to particular design implementations, with specific adaptions of the SRAM subsystem limiting, or even precluding, the scalability of the SRAM subsystem design. As a result SRAM memory subsystem designs, even those considered to be xe2x80x9cscalablexe2x80x9d, often fail to meet design limitations once these memory subsystem designs are scaled-up for use in a VLSI system with need for a greater memory cell population and/or density.
There is a need for an efficient, scalable, high-performance, low-power memory structure that allows a system designer to create a SRAM memory subsystem that satisfies strict constraints for device area, power, performance, noise sensitivity, and the like.
The present invention satisfies the above needs by providing a high-precision delay measurement circuit that delivers exceptionally accurate time measurement, for example, a half-gate delay. The high-precision delay measurement circuit can be realized with a multi-stage ring oscillator that can be coupled with multiple oscillation signal detectors, which can be counters and signal edge detection circuits, which respectively count the number of oscillations by the circuit, and determine the extent to which a particular oscillation signal propagated within the oscillator. Some of the oscillation counters, particularly those disposed between the stages of the oscillator are preferred to be dual-edge detection counters. The high precision delay measurement circuit can have a control signal output which can constrain a limited voltage swing signal.
The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the following drawings.